In solar cells, tweaking the tiniest of parts yields big jump in efficiency

January 20, 2012

(PhysOrg.com) -- By tweaking the smallest of parts, a trio of University at Buffalo engineers is hoping to dramatically increase the amount of sunlight that solar cells convert into electricity.

With military colleagues, the UB researchers have shown that embedding charged quantum dots into photovoltaic cells can improve electrical output by enabling the cells to harvest infrared light, and by increasing the lifetime of photoelectrons.

The research appeared online last May in the journal Nano Letters. The research team included Vladimir Mitin, Andrei Sergeev and Nizami Vagidov, faculty members in UB's electrical engineering department; Kitt Reinhardt of the Air Force Office of Scientific Research; and John Little and advanced nanofabrication expert Kimberly Sablon of the U.S. Army Research Laboratory.

Mitin, Sergeev and Vagidov have founded a company, OPtoElectronic Nanodevices LLC. (OPEN LLC.), to bring the innovation to the market.

The idea of embedding quantum dots into solar panels is not new: According to Mitin, scientists had proposed about a decade ago that this technique could improve efficiency by allowing panels to harvest invisible, infrared light in addition to visible light. However, intensive efforts in this direction have previously met with limited success.

The UB researchers and their colleagues have not only successfully used embedded quantum dots to harvest infrared light; they have taken the technology a step further, employing selective doping so that quantum dots within the solar cell have a significant built-in charge.

This built-in charge is beneficial because it repels electrons, forcing them to travel around the quantum dots. Otherwise, the quantum dots create a channel of recombination for electrons, in essence "capturing" moving electrons and preventing them from contributing to electric current.

The technology has the potential to increase the efficiency of solar cells up to 45 percent, said Mitin, a SUNY Distinguished Professor. Through UB's Office of Science, Technology Transfer and Economic Outreach (STOR), he and his colleagues have filed provisional patent applications to protect their technology.

"Clean technology will really benefit the region, the state, the country," Mitin said. "With high-efficiency solar cells, consumers can save money and providers can have a smaller solar field that produces more energy."

Mitin and his colleagues have already invested significant amounts of time in developing the quantum dots with a built-in-charge, dubbed "Q-BICs." To further enhance the technology and bring it to the market, OPEN LLC is now seeking funding from private investors and federal programs.

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27 comments

In other research, I've seen claims of large increases of efficiency, but the increase is only applicable to very inefficient cells. Will this increase the efficiency of the most efficient cells out there? I.e., will it be an actual increase in efficiency visible to the consumer? And will it be cost effective?

Combine this with the idea of solar paint; where you can paint on the solar collector to any surface, connect leads to it, and have power (imagine using this on an RV). There is a project for this, using paint; but I suggested using a clear varnish with reflective base, to increase the light absorbed by the solar elements. With the Q-BIC idea combined with this, we should be able to produce viable, inexpensive solar solutions in the near future.

Solar energy is diluted, unreliable and material hungry solution, the financial effectiveness of which is disputable at the most areas of world. It will remain so, even if the effectiveness of solar cells would raise to 100 percent and it cannot compete with cold fusion in nearly any aspect.

Solar energy is diluted, unreliable and material hungry solution, the financial effectiveness of which is disputable at the most areas of world. It will remain so, even if the effectiveness of solar cells would raise to 100 percent and it cannot compete with cold fusion in nearly any aspect.

Capturing infrared light seems to have a lot of potential to me. Infrared light travels though clouds. Therefor, infrared solar cells should be able to generate consistent power not matter the overcast.

The big problem with Solar Panels is that the manufacturers keep the prices high due to supply and demand problem in the market - the only option today is to do it by a DIY Solar Panels and build your own solar panels for 1/10th of the price

Solar energy is diluted, unreliable and material hungry solution, the financial effectiveness of which is disputable at the most areas of world. It will remain so, even if the effectiveness of solar cells would raise to 100 percent and it cannot compete with cold fusion in nearly any aspect.

Solar energy is diluted, unreliable and material hungry solution, the financial effectiveness of which is disputable at the most areas of world. It will remain so, even if the effectiveness of solar cells would raise to 100 percent and it cannot compete with cold fusion in nearly any aspect.

Cannot compete with cold fusion in ANY aspect? I would add one possible exception. Solar power is real.

Besides, solar power can split water. Then you have hydrogen and oxygen, which can be stored indefinitely, shipped, etc. The biggest impediment to wind, solar, wave and other intermittent power sources, is storage. Batteries weigh a lot, wear out, and use up too much power in the manufacturing process. Better to store hydrogen and oxygen for later use.

If we did have 100% efficient solar panels, cars could drive directly on solar power at noon with just the roof area covered. Not highway speed, but 4-5 kilowatts is plenty

At noon? You can get 400 watts from direct sun-light per square meter at noon (considering the 100% efficiency of solar cells). It may cover the consumption of PC, but definitely not a car, not to say about car with climatization. The average solar flux is 10x lower, though.

solar power can split water. Then you have hydrogen and oxygen, which can be stored indefinitely, shipped

So far the batteries are most effective way of energy storage. The hydrogen compressed at 700 bar collects 5.6 megajoules per litre, lithium air battery 9 megajoules per kilogram (and the density of lithium is 0.53 kg/liter, so that this energy density is comparable). But the efficiency of hydrogen conversion to electricity or back again is just 40%. 0.4 x 0.4 = 0.16, it means nearly 90% of hydrogen is wasted just for storage and the electric battery clearly wins in both effectiveness, both energy density achieved. The hydrogen based economy is just a hoax of researchers involved in it. We could use the carbon hydrides, i.e. the gasoline with the same efficiency.

One aspect of EVs running on solar PVs is duty cycle. While you may not be able to drive under solar power per se, think how cars are operated. Let's say you drive 1/2 hr to work, 1/2 hr back. You park it in sunlight for eight hours in between. If not dependent on solar alone, surely, this is an impressive range extender. Taking a sizable load off the Grid supplied charger.

Sorry, the energy flux from solar panel at the roof of car is in range of few dozens of watts, whereas the energy consumption of your car is in range of few dozens of kilowatts. We are talking here about difference at the range of three orders of magnitude. http://www.lowtec...e-o.htmlIf we take a life expectancy of 3 years (already quite optimistic for most gadgets) and a solar insolation of 900 kWh/m² (quite optimistic too, since these things are not lying on a roof), the result is 1,038 gram CO2 per kWh in the worst case scenario (high-efficient mono-crystalline cells produced in the US). That means that it is better for the environment to power a gadget with electricity generated by coal, rather than by a solar panel.

At noon? You can get 400 watts from direct sun-light per square meter at noon (considering the 100% efficiency of solar cells). It may cover the consumption of PC, but definitely not a car, not to say about car with climatization. The average solar flux is 10x lower, though.

You specified a 100% efficient solar panel, so that's what I assumed. You'd get over a kilowatt per square meter with a perfect solar panel.

But with 400 Watts per sq-m, you'd still be able to drive a car. Consider that the roof and hood area of your car is on the order of 5-6 sq-m which means that your power budget with the sun directly overhead would be over 2 kW.

Knowing the energy requirements of an electric car, for reference: http://kilowatt-h...watt-car one can see that such a car could happily maintain approximately 20 mph directly on the solar panels, and a lighter more efficient car could do much better.

Why would we take a life expectancy of 3 years? You car would certainly not be expected to fall to pieces in just three, and neither would the panels.

Let's say we have 5 square meters of solar panels laminated on top of the car, and we have an efficiency of 12% nominal, which means a peak power of roughly 600 Watts, and an average of 60 Watts at latitudes like New York. That gives us 1440 Wh of energy per day.

1.44 kWh requires roughly 4 times as much energy to be generated in a powerplant and transmitted to you, which means that you save 5.76 kWh : 6.67 kWh/kg = 863 grams of coal per day. Turned into carbon dioxide, that would be 3164 grams of CO2, or 2197 grams per kWh.

Given your figures, we'd make roughly 300 g/kWh over ten years, and save 2197 g/kWh compared to coal, and that's a reduction of 85%, or if you consider a mix of generation, it could still be over 50% less CO2/kWh.

It's one half of horse power (or the half of power of kitchen blender to express it in more contemporary units) - whereas the common cars consume dozens if not hundreds of horse power units. And 400 Watts is the theoretical maximum, in real case you can get only one tenth of this power. Actually it's quite easy: just demonstrate us some working project of solar car for everyday use and we can discuss about it. All these BS's are absolutely unnecessary if only the scientists would consider the cold fusion research responsibly. http://pesn.com/2...locaust/

In the best case scenario, one square meter of solar cells carries a burden of 75 kilograms of CO2. In the worst case scenario, that becomes 314 kilograms of CO2.

So, projected over 10 years, with an average of 1.44 kWh per day, we get 5256 kWh energy produced, and only 71 grams of CO2 per kilogram. The worst case scenario would be 300 g/kWh.

Even the worst case scenario produces less CO2 than power from the grid, with places like UK averaging 400 g/kWh. But in your worst case scenario you're really talking about places like Poland that average 800 g/kWh. Comparing apples to apples, it's easy to see that solar panels would easily remove over 50% of it in any case.

Calippo, your figures are wrong. Even your sources don't support your conclusions. Solar panels have favorable CO2 load compared to fossil fuels, and it's only getting better as more of the energy mix is being generated with renewable energy, further reducing the CO2 impact of solar.

It's one half of horse power (or the half of power of kitchen blender to express it in more contemporary units) - whereas the common cars consume dozens if not hundreds of horse power units.

How much a car consumes depends on the speed at which it is travelling, and how far you've jammed the gas pedal.

And kitchen blenders don't actually operate at 1 HP. That's just the maximum peak power that the motor is capable of - the rated power. For an electric car, you need roughly 20 HP to maintain highway speed, and 2-3 HP to roll along around the neighborhood.

OK, I'll say it even more quite clearly: the research of solar energy is OK like every basic research - but in the light of cold fusion finding is just another substituter of real solution, the only purpose is to keep the jobs and salaries of many people involved in it. All these people are therefore less or more directly responsible for the contemporary financial crisis, the rise of fossil fuel prices and for the risk of global nuclear war which is nearing. They're essentially behaving like the stupid and coward people in Nazi Germany, who voted for Hitler willingly because they followed their own private interests during this - and I really don't care, if they're able to recognize this analogy now or not.

What I'm missing is the responsible mature behavior of the layman society, which should be based on the seeking of the most effective and ecological energetic solution under all circumstances - and these circumstances are changing rapidly.

Which is most ironic with stance of Americans here is, they will help the China, not their country with their adherence on solar panel technologies, because the Chinese can produce these panels in much cheaper and effective way already and the China is already controlling the export of rare elements (indium), which are used during this. In this way, the solar industry is actually destroying the USA economy - but many Americans are stupid enough for not being able to recognize it. http://www.braden...roy.html